Glow plug quick heating control device

Abstract

A glow plug heating control device for a diesel engine includes a detector for detecting the heat variable resistance of the glow plug, and a device effecting insertion of a resistor in series with the glow plug and the power source at a given point so as to vary the manner of current application to and the heating of the plug in an advantageous non-linear manner.

What is claimed is: 
     
       1. A glow plug heating circuit for use with a glow plug having a heat generating element whose resistance varies with heating temperature comprising; a series connection of said glow plug, a power source, and a current detecting resistor, and switching means for inserting a voltage dropping resistor into said series circuit, so as to vary a current applied to said glow plug in a non-linear manner, wherein said voltage dropping resistor includes a heat generating element the temperature coefficient of which is equal to that of said heat generating element of said glow plug. 
     
     
       2. A control device with a glow plug heating circuit in which a glow plug having a heat generating element whose resistance varies with heating temperature, a current detecting resistor, and a switching unit are connected in series with a power source, comprising: means for determining the resistance of said heat generating element according to a voltage developed across said current detector resistor;   comparator means for providing an output signal when said determined value reaches a set value correspondingly smaller than a predetermined preheating temperature; and   switching unit driving means for operating said switching unit in response to an output of said comparator, to open said glow plug heating circuit and to insert a voltage dropping resistor in series in said heating circuit to complete said heating circuit, wherein said voltage dropping resistor includes a heat generating element, the temperature coefficient of which is equal to that of said heat generating element of said glow plug.   
     
     
       3. A control resistor for use with a glow plug, comprising: a coil including at least two series connected resistance wires having different resistance/temperature characteristics wherein the resistance of said wires substantially equals the resistance of an element of said glow plug; and   an insulating material surrounding said coil.   
     
     
       4. A control device as claimed in claim 2, said voltage dropping resistor being installed on a cylinder block of said engine so that the temperature of said resistor varies in accordance with the temperature variation of said engine block. 
     
     
       5. A control device as claimed in claim 2, said switching unit driving means including relay drive circuit means responsive to said comparator output for operating a first relay to open said heating circuit, and timer means for activating a second relay for a predetermined time to connect said voltage dropping resistor in said heating circuit. 
     
     
       6. A control device as claimed in claim 2, said determining means including a bridge circuit including the resistance of the glow plug and said current detecting resistor. 
     
     
       7. A control device as claimed in claim 2, said voltage dropping resistor including at least two series connected resistance wires having differing resistance/temperature coefficients. 
     
     
       8. A device as claimed in claim 2, said resistor having a temperature coefficient substantially equal to that of an element of said glow plug. 
     
     
       9. A glow plug heating circuit as recited in claim 1, wherein said heat generating element comprises at least two series connected resistance wires having different resistance/temperature coefficients.